In situcharacterization of the thermal state of resonant optical interferometers via tracking of their higher-order mode resonances. Mueller, C. L.; Fulda, P.; Adhikari, R. X.; Arai, K.; Brooks, A. F.; Chakraborty, R.; Frolov, V. V.; Fritschel, P.; King, E. J.; Tanner, D. B.; Yamamoto, H.; and Mueller, G. Classical and Quantum Gravity, 32(13):Art. No. 135018, Institute of Physics, July, 2015. o̧pyright 2015 IOP Publishing Ltd. Received 16 February 2015, revised 23 April 2015; Accepted for publication 30 April 2015; Published 12 June 2015.
In situcharacterization of the thermal state of resonant optical interferometers via tracking of their higher-order mode resonances [link]Paper  abstract   bibtex   
Thermal lensing in resonant optical interferometers such as those used for gravitational wave detection is a concern due to the negative impact on control signals and instrument sensitivity. In this paper we describe a method for monitoring the thermal state of such interferometers by probing the higher-order spatial mode resonances of the cavities within them. We demonstrate the use of this technique to measure changes in the advanced LIGO (aLIGO) input mode cleaner cavity geometry as a function of input power, and subsequently infer the optical absorption at the mirror surfaces at the level of 1 ppm per mirror. We also demonstrate the generation of a useful error signal for the thermal state of the aLIGO power recycling cavity by continuously tracking the first order spatial mode resonance frequency. Such an error signal could be used as an input to thermal compensation systems to maintain the interferometer cavity geometries in the presence of transients in circulating light power levels, thereby maintaining optimal sensitivity and maximizing the duty-cycle of the detectors.
@article{caltechauthors58963,
	Abstract = {Thermal lensing in resonant optical interferometers such as those used for gravitational wave detection is a concern due to the negative impact on control signals and instrument sensitivity. In this paper we describe a method for monitoring the thermal state of such interferometers by probing the higher-order spatial mode resonances of the cavities within them. We demonstrate the use of this technique to measure changes in the advanced LIGO (aLIGO) input mode cleaner cavity geometry as a function of input power, and subsequently infer the optical absorption at the mirror surfaces at the level of 1 ppm per mirror. We also demonstrate the generation of a useful error signal for the thermal state of the aLIGO power recycling cavity by continuously tracking the first order spatial mode resonance frequency. Such an error signal could be used as an input to thermal compensation systems to maintain the interferometer cavity geometries in the presence of transients in circulating light power levels, thereby maintaining optimal sensitivity and maximizing the duty-cycle of the detectors.},
	Author = {Chris L. Mueller and Paul Fulda and Rana X. Adhikari and Koji Arai and Aidan F. Brooks and Rijuparna Chakraborty and Valery V. Frolov and Peter Fritschel and Eleanor J. King and David B. Tanner and Hiroaki Yamamoto and Guido Mueller},
	Journal = {Classical and Quantum Gravity},
	Keywords = {gravitational wave, interferometers, thermal lensing, LIGO},
	Month = {July},
	Note = {{\copyright} 2015 IOP Publishing Ltd. Received 16 February 2015, revised 23 April 2015; Accepted for publication 30 April 2015; Published 12 June 2015.},
	Number = {13},
	Pages = {Art. No. 135018},
	Publisher = {Institute of Physics},
	Title = {In situcharacterization of the thermal state of resonant optical interferometers via tracking of their higher-order mode resonances},
	Url = {http://resolver.caltech.edu/CaltechAUTHORS:20150721-111255136},
	Volume = {32},
	Year = {2015},
	Bdsk-Url-1 = {http://resolver.caltech.edu/CaltechAUTHORS:20150721-111255136}}
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